Is this an equivalent formula for P(A or B or C) ?

[opticaltempest]

I was trying to derive a formula to find P(A \cup B \cup C).

I came up with the following:

http://img249.imageshack.us/img249/2154/probabilitymp7.jpg

Is that correct?

[IMDerek]

Yes it's correct

[ZioX]

See Principle of Inclusion-Exclusion for the general result.

http://en.wikipedia.org/wiki/Inclusion_exclusion